Seeking advice on Extending Low-Frequency Response in 70's speakers

[holdingpants01]

I would still recommend adding a sub, however:
1. it's not as easy as you think, so there's something to learn while doing it trying crossovers, delays, phase rotations etc.
2. you won't loose any resale value, modified speakers are worth basically nothing on the used market
3. you have much bigger chance of success of it being at least listenable
4. another upside is the final result which would be better with a subwoofer or two, than anything you could do modifying the speakers
5. and most importantly you can still do digital crossover, improve the whole range and tweak the whole system to your liking without changing any driver, so it still looks the same and is easily reversible

 

[mhardy6647]

Extended LF from old loudspeakers?
Stick the loudspeakers in the corners of a room.

 

[DanielT]

So, if I understood it all correctly, you have bought : To test this theory, I got my hands on a pair of 488s

Are these 488, or 22AH488 (also marketed as the 22AH468, which has a different look) fully functional?

Then you have two pairs of speakers. A pair of Philips 22AH487, with bass driver with passive radiator and a pair of Philips 22AH488/22AH468 with
double bass drivers. Is it true so far?

Your two pairs of speakers seem to have the same mid drivers and tweeters. Why not keep 22AH488/ 22AH468 as it is? Have you measured your 22AH488/22AH468?

Philips 22AH468:

Philips 22AH487:


Edit:
Or do you mean that you only got hold of new bass drivers? Four pieces or two AD8067? If you have got hold of four, why not remove the passive radiators and install the four bass drivers in your boxes? Then you have some power to play with and then EQ and raise the frequency a little at the bottom where they start to roll off.

Maybe you can test with a Linkwitz transform compensated bass system if you have sealed boxes? Note that I have never tested a Linkwitz transformation myself. In that case, others can give you tips and advice about that:

Linkwitz Transform

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www.minidsp.com

 

[alex-z]

Adding mass to the passive radiator would drop the tuning frequency. However the excursion will increase, so a single PR is likely insufficient, the speaker would have reduced peak SPL. The enclosure volume may also be insufficient, causing the PR efficiency to drop.

Bracing would almost certainly improve bass and mid-bass quality but not help bass extension.

Minor air leaks would not significantly change the bass response. They usually show up in impedance sweeps if you want to check for them.

Overall, adding a sub is the easiest and best solution. BK Elec offers wood finishes if you want to match the aesthetic without a DIY build.

Sub Woofers - Sub Bass - Subwoofer

You mentioned running a DSP 3 way crossover. This won't increase bass extension but will significantly improve the overall performance. Better management of driver breakup modes, no distortion or wasted power from passive crossover components, EQ to pull down room mode peaks, etc.

 

[Wafoe]

Cheers to the new year. Thanks again everyone for your advice. I did some more research these holidays and I'd like to share where I'm at right now and respond to some of your comments.

So, if I understood it all correctly, you have bought : To test this theory, I got my hands on a pair of 488s

Are these 488, or 22AH488 (also marketed as the 22AH468, which has a different look) fully functional?

Then you have two pairs of speakers. A pair of Philips 22AH487, with bass driver with passive radiator and a pair of Philips 22AH488/22AH468 with
double bass drivers. Is it true so far?

Yes, what you interpreted is correct.

I obtained two defective pairs of 22AH468 for cheap. I managed to fully repair one pair. The mids didn't work, but were easily fixable following this writeup. It's a common defect with these units. The second pair has one non-repairable blown mid and someone replaced one of the woofers with a random aftermarket unit, so I can't bring this pair back to original form without additional units sourced from somewhere.

Your two pairs of speakers seem to have the same mid drivers and tweeters. Why not keep 22AH488/ 22AH468 as it is? Have you measured your 22AH488/22AH468?

Edit:
Or do you mean that you only got hold of new bass drivers? Four pieces or two AD8067? If you have got hold of four, why not remove the passive radiators and install the four bass drivers in your boxes? Then you have some power to play with and then EQ and raise the frequency a little at the bottom where they start to roll off.

Maybe you can test with a Linkwitz transform compensated bass system if you have sealed boxes? Note that I have never tested a Linkwitz transformation myself. In that case, others can give you tips and advice about that:

The mids are the same, but the tweeters are the 15 Ohm variant (AD0163/T15), which should be about 3 dB less efficient than the 8 Ohm variant (AD0163/T8) in the 22AH487.

I measured the in-room frequency response of the now working pair 22AH468. They're okay but have a strong v-shaped sound signature. The lows have a lot of weird 'wobbly' distortion with my (admittedly sub-par) Denon UDRA-F07 amp, possibly because of the protective car lamps in the crossover filter. Bass is slightly stronger than the 22AH487s but not deeper without EQ. Probably because the 35 L box is too small for the two 8-inch AD8067/W4E woofers.

Overall, not impressed with the sound signature. And I don't dig their box design, which was my main motivator for starting this project on modifying the 22AH487 speakers.

----------

To end the speculation on what combination of drivers is most effective, I’ve decided to seek concrete answers by learning how to measure T/S parameters myself. I've researched the process, ordered the necessary components, and plan to conduct my own measurements of all the drivers with REW. Once I have the data, I'll use recommended speaker design software to evaluate whether a PR system would be effective for the AD8067/W4E, or if it would be better to simply use dual woofers with additional power compensation for lower frequencies. I can use the drivers sourced from the (defective) 22AH468 units for this.

----------

Since I'm already planning to modify the speakers anyways, I want to go all the way with improving the sonic quality of them. I.e. I've already found that the driver break-up modes are not suppressed and I doubt the drivers are phase aligned on the baffle.

• To address panel vibrations, I’ve ordered bitumen sheets (instead of adding bracing, as I want to preserve the internal volume of the enclosures). I’ve also ordered felt for lining the walls and glass wool to dampen the back wave of the woofer(s). The goal of this isn’t to achieve deeper bass but to improve its quality, like alex-z said. The original synthetic dampening material in the 22AH487s has completely degraded and needs to be replaced anyways.
• Additionally, I plan to follow through with an active DSP crossover for its inherent advantages and as a personal learning opportunity. To support this, I’ll add a 6-pin DIN socket, allowing individual amplifier channels to connect to each driver (or in the case of the woofer, either one, or two in series). I also consider including a triple-pole, double-throw switch to retain the option of using the original crossover, should I want to revert to the classic setup in the future. I've created a wiring diagram for this plan, but I’d appreciate it if someone could verify its accuracy:
  
  
  
  
• To support an active crossover project, I found several product options. Honestly, I don't really know what would be the easiest for a beginner like me, and has the best bang/buck. I can source cheaply from Chinese Taobao. I plan to use either:
  • A Raspberry Pi running CamillaDSP, combined with a Creative Sound Blaster Omni Surround 5.1 external DAC I have lying around. For amplification, I'm thinking about either:
    • A cheap 7.1 receiver I can source second hand (quality varies)
    • A 6 channel TPA3255-based board (should perform quite nicely for the budget)
    • A 8 channel Wondom KAB9 board (I haven't found measurements)
  • 2x Wondom JAB5 boards hooked up together (master-slave), which have the ADAU1701 DSP built in and 4 amplifier channels each (4x100W). Maybe the neatest and easiest. Don't know about the quality of the DACs and amplification though.
  • I can also use an ADAU1562 DSP board with an AD1938 or CS42448 codec instead of the Raspberry Pi + multichannel DAC. Combined with one of the aforementioned amplification options.

Let me know your thoughts.

 

[Vladimir Filevski]

the bass response is disappointing, especially considering the size of the enclosure... 8-inch woofer and an 8-inch passive radiator, but the bass rolls off sharply at around 50 Hz (48 dB/octave),

This behavior is typical for a passive radiator loudspeaker - it can not be made better.

My idea is to combine the best parts of the 487 and 488 designs:

Do not change drivers with different ones and do not mess with the passive radiator, PLEASE!
Just replace old bipolar electrolytic capacitors with new ones.
If you need deeper bass, buy a subwoofer.

 

[DanielT]

Cheers to the new year. Thanks again everyone for your advice. I did some more research these holidays and I'd like to share where I'm at right now and respond to some of your comments.


Yes, what you interpreted is correct.

I obtained two defective pairs of 22AH468 for cheap. I managed to fully repair one pair. The mids didn't work, but were easily fixable following this writeup. It's a common defect with these units. The second pair has one non-repairable blown mid and someone replaced one of the woofers with a random aftermarket unit, so I can't bring this pair back to original form without additional units sourced from somewhere.


The mids are the same, but the tweeters are the 15 Ohm variant (AD0163/T15), which should be about 3 dB less efficient than the 8 Ohm variant (AD0163/T8) in the 22AH487.

I measured the in-room frequency response of the now working pair 22AH468. They're okay but have a strong v-shaped sound signature. The lows have a lot of weird 'wobbly' distortion with my (admittedly sub-par) Denon UDRA-F07 amp, possibly because of the protective car lamps in the crossover filter. Bass is slightly stronger than the 22AH487s but not deeper without EQ. Probably because the 35 L box is too small for the two 8-inch AD8067/W4E woofers.

Overall, not impressed with the sound signature. And I don't dig their box design, which was my main motivator for starting this project on modifying the 22AH487 speakers.

----------

To end the speculation on what combination of drivers is most effective, I’ve decided to seek concrete answers by learning how to measure T/S parameters myself. I've researched the process, ordered the necessary components, and plan to conduct my own measurements of all the drivers with REW. Once I have the data, I'll use recommended speaker design software to evaluate whether a PR system would be effective for the AD8067/W4E, or if it would be better to simply use dual woofers with additional power compensation for lower frequencies. I can use the drivers sourced from the (defective) 22AH468 units for this.

----------

Since I'm already planning to modify the speakers anyways, I want to go all the way with improving the sonic quality of them. I.e. I've already found that the driver break-up modes are not suppressed and I doubt the drivers are phase aligned on the baffle.

• To address panel vibrations, I’ve ordered bitumen sheets (instead of adding bracing, as I want to preserve the internal volume of the enclosures). I’ve also ordered felt for lining the walls and glass wool to dampen the back wave of the woofer(s). The goal of this isn’t to achieve deeper bass but to improve its quality, like alex-z said. The original synthetic dampening material in the 22AH487s has completely degraded and needs to be replaced anyways.
• Additionally, I plan to follow through with an active DSP crossover for its inherent advantages and as a personal learning opportunity. To support this, I’ll add a 6-pin DIN socket, allowing individual amplifier channels to connect to each driver (or in the case of the woofer, either one, or two in series). I also consider including a triple-pole, double-throw switch to retain the option of using the original crossover, should I want to revert to the classic setup in the future. I've created a wiring diagram for this plan, but I’d appreciate it if someone could verify its accuracy:
  View attachment 418625
• To support an active crossover project, I found several product options. Honestly, I don't really know what would be the easiest for a beginner like me, and has the best bang/buck. I can source cheaply from Chinese Taobao. I plan to use either:
  • A Raspberry Pi running CamillaDSP, combined with a Creative Sound Blaster Omni Surround 5.1 external DAC I have lying around. For amplification, I'm thinking about either:
    • A cheap 7.1 receiver I can source second hand (quality varies)
    • A 6 channel TPA3255-based board (should perform quite nicely for the budget)
    • A 8 channel Wondom KAB9 board (I haven't found measurements)
  • 2x Wondom JAB5 boards hooked up together (master-slave), which have the ADAU1701 DSP built in and 4 amplifier channels each (4x100W). Maybe the neatest and easiest. Don't know about the quality of the DACs and amplification though.
  • I can also use an ADAU1562 DSP board with an AD1938 or CS42448 codec instead of the Raspberry Pi + multichannel DAC. Combined with one of the aforementioned amplification options.

Let me know your thoughts.

If you want better bass, without a sub, you don't have much other option, if you want to keep the speaker boxes, then to put another modern 8 inch bass driver in them. BUT it leads to a different appearance of the speakers. You also have to find suitable passive radiator or convert them to sealed or ported, suitable crossover to mids is needed and so on. Nah, it's just too much backward work, hassle (as the farmer who sheared the pig said:that was much cry for little wool ) Then you might as well buy a couple of other speakers and compare with.

You see, no matter how you twist and turn it with your requests for bass below 50 Hz, you end up back at square 1, as pointed out by several others: Add a subwoofer.

Edit:
You liked the idea of having two bass boxes, subwoofers in the same style/looks like your speakers as a stand but you didn't have the opportunity to build them yourself. Proposal:Let some local small carpentry saw plywood boards, plus holes for mounting sub drivers, elements. Then glue and or screw the pieces together yourself? Surface finish that matches, easiest if you're lucky some plastic veneer that looks like your speakers that you just put on the boxes.

 

[DanielT]

Cheers to the new year. Thanks again everyone for your advice. I did some more research these holidays and I'd like to share where I'm at right now and respond to some of your comments.


Yes, what you interpreted is correct.

I obtained two defective pairs of 22AH468 for cheap. I managed to fully repair one pair. The mids didn't work, but were easily fixable following this writeup. It's a common defect with these units. The second pair has one non-repairable blown mid and someone replaced one of the woofers with a random aftermarket unit, so I can't bring this pair back to original form without additional units sourced from somewhere.


The mids are the same, but the tweeters are the 15 Ohm variant (AD0163/T15), which should be about 3 dB less efficient than the 8 Ohm variant (AD0163/T8) in the 22AH487.

I measured the in-room frequency response of the now working pair 22AH468. They're okay but have a strong v-shaped sound signature. The lows have a lot of weird 'wobbly' distortion with my (admittedly sub-par) Denon UDRA-F07 amp, possibly because of the protective car lamps in the crossover filter. Bass is slightly stronger than the 22AH487s but not deeper without EQ. Probably because the 35 L box is too small for the two 8-inch AD8067/W4E woofers.

Overall, not impressed with the sound signature. And I don't dig their box design, which was my main motivator for starting this project on modifying the 22AH487 speakers.

----------

To end the speculation on what combination of drivers is most effective, I’ve decided to seek concrete answers by learning how to measure T/S parameters myself. I've researched the process, ordered the necessary components, and plan to conduct my own measurements of all the drivers with REW. Once I have the data, I'll use recommended speaker design software to evaluate whether a PR system would be effective for the AD8067/W4E, or if it would be better to simply use dual woofers with additional power compensation for lower frequencies. I can use the drivers sourced from the (defective) 22AH468 units for this.

----------

Since I'm already planning to modify the speakers anyways, I want to go all the way with improving the sonic quality of them. I.e. I've already found that the driver break-up modes are not suppressed and I doubt the drivers are phase aligned on the baffle.

• To address panel vibrations, I’ve ordered bitumen sheets (instead of adding bracing, as I want to preserve the internal volume of the enclosures). I’ve also ordered felt for lining the walls and glass wool to dampen the back wave of the woofer(s). The goal of this isn’t to achieve deeper bass but to improve its quality, like alex-z said. The original synthetic dampening material in the 22AH487s has completely degraded and needs to be replaced anyways.
• Additionally, I plan to follow through with an active DSP crossover for its inherent advantages and as a personal learning opportunity. To support this, I’ll add a 6-pin DIN socket, allowing individual amplifier channels to connect to each driver (or in the case of the woofer, either one, or two in series). I also consider including a triple-pole, double-throw switch to retain the option of using the original crossover, should I want to revert to the classic setup in the future. I've created a wiring diagram for this plan, but I’d appreciate it if someone could verify its accuracy:
  View attachment 418625
• To support an active crossover project, I found several product options. Honestly, I don't really know what would be the easiest for a beginner like me, and has the best bang/buck. I can source cheaply from Chinese Taobao. I plan to use either:
  • A Raspberry Pi running CamillaDSP, combined with a Creative Sound Blaster Omni Surround 5.1 external DAC I have lying around. For amplification, I'm thinking about either:
    • A cheap 7.1 receiver I can source second hand (quality varies)
    • A 6 channel TPA3255-based board (should perform quite nicely for the budget)
    • A 8 channel Wondom KAB9 board (I haven't found measurements)
  • 2x Wondom JAB5 boards hooked up together (master-slave), which have the ADAU1701 DSP built in and 4 amplifier channels each (4x100W). Maybe the neatest and easiest. Don't know about the quality of the DACs and amplification though.
  • I can also use an ADAU1562 DSP board with an AD1938 or CS42448 codec instead of the Raspberry Pi + multichannel DAC. Combined with one of the aforementioned amplification options.

Let me know your thoughts.

Crossover via DSP, so you can choose the crossover point yourself plus measure FR with an microphone. With that, changes can definitely happen. Measure each driver and see how they behave. An interesting aspect is how the midrange FR looks higher up in frequency, so maybe you can change the crossover point for the better. Perhaps. Maybe not, but you'll notice when you test.

One thing you should think about is C-C in relation to the crossover point between mid and tweeter. See what the creator of VituixCAD Loudspeaker simulator

VituixCAD Loudspeaker simulator

....Kimmosto writes about it here:

Minimum c-c is 1.0 x wave length and maximum about 1.4 x wave length at XO frequency assuming that design is conventional uni-directional box (not open baffle) with phase matching (acoustical 4th order) slopes. Good and quite flexible initial/design value for c-c is 1.2 x wave length at XO, giving smooth combination of power and early reflections i.e. balanced sound without significant power dip at XO due to bump in DI and dip in vertical early reflections. In other words, this concept aims lobe nulls to directions which are the least significant for power response and vertical early reflections - and listener sitting in sweet spot of course.

Some help with lobing

I think I understand the concept but can't figure out the solution. "Lobing occurs with any two drivers producing the same frequency range in parallel (identical signal) where the distance between the drivers is greater than 1/4 wavelength of any frequency they are reproducing." So if I am...

audiosciencereview.com

 

[Head_Unit]

(instead of adding bracing, as I want to preserve the internal volume of the enclosures

Use like 1/2"x1/2" square dowels, the impact on internal volume would be about nothing. Round dowels can work, but square dowels give the option to glue together in the middle. For instance front-to-back, side-to-side, top-to-bottom all touching and glued together in the center. Especially if the enclosures are kind of thinwall this will help a lot. Cool project!

Now if you stuffed the enclosure (maybe 1.3 pounds fiberglass per cubic foot of enclosure...Vance Dickason's seminal Loudspeaker Cookbook has a whole chapter) that both absorbs more midrange internally and can make the enclosure appear larger internally. That will shift the tuning a tad lower, and if you added some mass to the passive radiator it would shift lower some more. That should result in some more low frequency output, though way below 50 Hz I dunno about that. And if you're changing drivers then it's a whole different story.

 

[dualazmak]

Sorry to be late coming here...

I agree with many friends on this thread recommending addition of subwoofer(s).

Furthermore, if you would be "brave" enough, you may convert your SPs into fully active multichannel configuration by eliminating/bypassing all the passive LC(R) network (and attenuators, if you have) so that each of the SP drivers will be driven by each of the multiple amplifiers in each of the XO-ed (cross-overed) frequency ranges done in upstream digital domain by DSP software within PC (or Mac).

In this case, you can also achieve precise time-alignment between all the SP drivers (measured and tuned for your listening position) by the upstream DSP software.

I have done all of these on my rather vintage(?) but still extremely excellent SP drivers and cabinet of YAMAHA NS-1000 (not NS-1000M) plus L&R subwoofers and L&R super-tweeters, as fully shared on my project thread. If you would be interested, please visit my post #931 there for details of the latest system setup.

As for your possible addition of subwoofer(s), these thread and posts would be of your reference, I assume;

- An Attempt Sharing Reference Quality Music Playlist: at least a portion and/or whole track being analyzed by 3D color spectrum of Adobe Audition
- [Part-09] Organ Music

- A nice smooth-jazz album for bass (low Fq) and higher Fq tonality check and tuning

 

[dualazmak]

• Additionally, I plan to follow through with an active DSP crossover for its inherent advantages and as a personal learning opportunity. To support this, I’ll add a 6-pin DIN socket, allowing individual amplifier channels to connect to each driver (or in the case of the woofer, either one, or two in series). I also consider including a triple-pole, double-throw switch to retain the option of using the original crossover, should I want to revert to the classic setup in the future. I've created a wiring diagram for this plan, but I’d appreciate it if someone could verify its accuracy:
  
  

This idea/plan of yours is basically identical to my implementation; in my case, I dare to use L&R screw-cable-SP-wiring-board for this purpose; you may find the latest "SP-cabling-boards" here #976 on my project thread.

I would like to remind you that you should carefully avoid/eliminate any of magnetic-susceptible metals, including the toggle switches, in this type of "SP-high-level-signal handling".
- Elimination of magnetic susceptible metals in SP signal handling: #250, #013(remote thread)
In my post #931, I also wrote as follows under the below spoiler cover;

Spoiler

I still keep the currently-not-in-use "LCR passive network in outer-box " (ref. #5) for easy and smooth role back of the whole audio system into my reference single-amplifier (ACCUPHASE E-460) passive configuration together with the connection changes on the "SP cabling boards".

I once have tested “Multi-Terminal Electromagnetic Relay” and “Multi-Terminal Snap-Toggle Switch” for this purpose (i.e. switching the wires between passive and active SP modes), but I found they gave some “uncleanliness and/or distortions” to the total sound. Consequently, I believe that the “physical screw-up cabling connections” like in these SP cabling boards should be the best way to go with. I carefully and completely eliminated, therefore, any magnetic susceptible (magnetizable) metal, such as screws, Y-lugs, metal plate on terminal straps, etc. in SP high-level signal wiring; please refer to my post #4, #250 and posts #013(remote thread), #023(remote thread) and here #9(remote thread).

You would please be reminded "the typical issue case" in this regard (even with no relation at all to my project thread) happened with first version of BUCKEYE 3 Channel Purifi Amplifier in which measurable (and I think audible) distortion was caused by iron (steel) plates at the SP binding posts, then BUCKEYE quickly and nicely replaced the parts with brass plates by a kind of recall announcement; please refer to the specific thread on that amplifier, amirm’s first review pointing the issue, as well as his second preferrable review on the fixed/revised amplifier.

Furthermore, in my post #9 on a remote thread "Ferromagnetic materials in audio connectors", I also wrote as follows;
If you take a look inside some rather high-end HiFi amplifiers, you'll see that the SP output wiring (and power wiring?) uses non-magnetic terminals and screws made of brass (no iron at all) or pure copper. However, this is also a common-sense measure to prevent sound quality deterioration in HiFi amplifiers. I remember it being pointed out and explained in interviews with a Yamaha amplifier designer and a Rotel engineer. It is frustrating when working with magnetized screwdrivers (screwdrivers) because you can't catch the screws, though. Yamaha's and Rotel's amplifier designers had a hard time persuading the assembly workers at the amplifier factories, but in the end, they convinced them to use non-magnetic terminals and screws, giving priority to sound quality; I've also heard that the screwdriver, which uses a chuck to fix screws and bolts to the tip, was devised so that it could be used in factories. In my DIY audio setup, I have the same thing; I strictly/completely eliminate/avoid any magnetizable metal/screw in my SP cabling/connecting.

 

[Head_Unit]

In the 70s, speaker design often relied on trial and error, with less advanced measurement techniques, which sometimes led to sub-optimal performance.

Yup. Dog bless Thiele and Small (and Benson!) and then LEAP and LMS.
- In-room response is cute but it is influenced by the ROOM. Please run a near-field curve of the woofer and radiator, with the microphone so close it is almost hitting. THAT is the actual response of the speaker by itself.
- I would recommend stuffing the enclosures, which will make them seem larger, and lower the effective tuning of the radiator some. This will absorb midrange from the back of the woofer but more to your need will extend the lowest frequencies at some expense to the midbass. How much? Ah, there's a question!
- Do you have a way to measure the impedances? You can get this little gizmo if you really want to go all-in. With this data some kind folks either here or at
https://www.avsforum.com/forums/diy-speakers-and-subs.155/
https://www.diyaudio.com/community/forums/subwoofers.63/
could run simulations and tell you really what will happen, particularly the adding mass part if you want to do that. (Offhand I think the stuffing, which can raise apparent box volume by up to 25-40%, would be enough of that).
- While you're at it if you coat the insides of the cabinets with anti-resonance goop that can improve those ole vintage cabs. Maybe from here http://cascadeaudio.com And add some cross-bracing inside, dowels top-to-bottom, side-to-side, front-to-back. Tiny square ones can meet in the center and be all tied together without affecting cabinet volume significantly.
I did all that stuff to my best friend's husband's vintage speakers. Even as a loudspeaker engineer I was literally shocked how much better they sounded.

 

[DanielT]

I was lucky. Bought a pair of vintage Infinity 1500e from an older man who just wants to get rid of them and other speakers. It was a really good bargain. Total $70 for four pairs of speakers (including a pair of Kef Coda 7).

Fun to test. I'll be selling some of them later this summer/fall. Anyway, considering the topic of this thread about bass. These Infinity 1500e; sealed boxes, around 40 liter box. Classic 8 inch paper-based cone woofer. Most likely minimal stroke/x-max. Bass, well not much to cheer about.
So what to do? In with them in the corners of the summer cottage where I am now. Yep better, around 6 dB (theoretically) more bass boost. Plus, since it's a sealed box (that seems to roll off high up in frequency) it's possible to EQ. Very rudimentary EQ boost done. Result? Almost too much. No deep bass but more midbass/lower midbass. I don't try to "force" more output from them below, say, 45 Hz. The little it would gain would undoubtedly be outweighed by a significantly reduced SPL/increased distortion. Beyond that, I won't go into the acoustic disadvantages, beyond bass, that come with squeezing speakers into corners.

It's just a test. It will end up with me plugging in my subwoofer with a built-in HP-LP filter (80 Hz should be good) and then placing the speakers more optimally in my living room.
If I don't prioritize painting the pine paneling white instead, then it will be an empty room and headphones for a while to come.
(The speaker outputs/speaker terminal in the wall don't work. It's been years since mice chewed through those cables behind the wall panel.)

Edit:
I have now changed the price to the correct one: $70 total for four pairs. I accidentally wrote $700 in the post.

Edit 2:
Now with a sub plus better placement of the speakers, like day and night in sound difference. And then I haven't even dampened reflections from the large windows, still a huge difference.

 

[DanielT]

OI was lucky. Bought a pair of vintage Infinity 1500e from an older man who just wants to get rid of them and other speakers. It was a really good bargain. Total $70 for four pairs of speakers (including a pair of Kef Coda 7).

Fun to test. I'll be selling some of them later this summer/fall. Anyway, considering the topic of this thread about bass. These Infinity 1500e; sealed boxes, around 40 liter box. Classic 8 inch paper-based cone woofer. Most likely minimal stroke/x-max. Bass, well not much to cheer about.
So what to do? In with them in the corners of the summer cottage where I am now. Yep better, around 6 dB (theoretically) more bass boost. Plus, since it's a sealed box (that seems to roll off high up in frequency) it's possible to EQ. Very rudimentary EQ boost done. Result? Almost too much. No deep bass but more midbass/lower midbass. I don't try to "force" more output from them below, say, 45 Hz. The little it would gain would undoubtedly be outweighed by a significantly reduced SPL/increased distortion. Beyond that, I won't go into the acoustic disadvantages, beyond bass, that come with squeezing speakers into corners.

It's just a test. It will end up with me plugging in my subwoofer with a built-in HP-LP filter (80 Hz should be good) and then placing the speakers more optimally in my living room.
If I don't prioritize painting the pine paneling white instead, then it will be an empty room and headphones for a while to come.
(The speaker outputs/speaker terminal in the wall don't work. It's been years since mice chewed through those cables behind the wall panel.)
View attachment 450832View attachment 450833

Edit:
I have now changed the price to the correct one: $70 total for four pairs. I accidentally wrote $700 in the post.

Edit 2:
Now with a sub plus better placement of the speakers, like day and night in sound difference. And then I haven't even dampened reflections from the large windows, still a huge difference.
View attachment 450925

Sometimes the conditions are just such that further good bass quite far down in frequency is impossible because of the driver. In the picture, the 8 inch with the small magnet in the Infinity 1500e, the other 8 inch, Seas 21 REX/DD. There is nothing special about the Seas bass driver, the 1500e bass driver on the other hand is far too powerless, too small a motor. The only advantage I can think of is a minimal x-max which might facilitate a slightly higher crossover point. Maybe with the paper membrane the break-ups are not so nasty, but bass: no way.

In other words, back to square one again: add a subwoofer.

 

[Roy_D]

I have a pair of 22AH486 which after dusting off from the garage and hooking up were a decent surprise but after 40+ years the caps in any speaker crossover warrant inspection and oftentimes replacing. Degraded caps in filters will have a huge impact on the overal sound, especially in bass.
That and adding a subwoofer would what I would do. The style of these Philips is not something you can buy new no =]
Maybe invest some time in finding a vintage piece of furniture that has the same veneer as the Philips you can make a cabinet out of for a modern subwoofer.

 

[Wafoe]

Time for another short update. Really appreciate all the responses, I've already learned so much.

I ended up making a measurement jig and measuring the T/S parameters of the (supposedly 'better') AD8067/W4E woofer. Measuring with REW, dual added mass, net me these results:

Philips AD8067/W4E woofer​

RE: 4.005 ohm
fS: 42.4 Hz
MMS: 18.69 g
Zmin: 4.504 ohm
QMS: 3.453
CMS: 0.754 mm/N
fmin: 168 Hz
QES: 0.586
RMS: 1.442 kg/s
f3: 759 Hz
QTS: 0.501
VAS: 55.50 litres
LE (f3): 0.633 mH
FTS: 84.7 Hz
Bℓ: 5.836 Tm
Dd: 17.00 cm
LP: 90.72 dB (1W/1m)
Eta: 0.71 %
Sd: 227.0 cm2
m1: 5.060 g
m2: 10.180 g

Philips AD8066/W4 woofer​

RE: 3.843 ohm
fS: 52.1 Hz
MMS: 15.61 g
Zmin: 4.197 ohm
QMS: 3.252
CMS: 0.597 mm/N
fmin: 249 Hz
QES: 0.726
RMS: 1.572 kg/s
f3: 1,195 Hz
QTS: 0.594
VAS: 43.67 litres
LE (f3): 0.369 mH
FTS: 87.8 Hz
Bℓ: 5.201 Tm
Dd: 17.00 cm
LP: 91.33 dB (1W/1m)
Eta: 0.83 %
Sd: 227.0 cm2
m1: 10.250 g
m2: 5.470 g

So my theory is correct: the AD8067/W4E is better suited towards bass response. Great! However, playing around with box tuning in VituixCAD in the existing 35 L enclosure, I couldn't find any PR configuration that would net a significantly deeper bass response. The box needs to be vastly bigger to get any improvement. Makes sense considering the QTS. It appears that you all are correct. There's really no way, other than changing drivers, to make a PR system work in this box.

Anyways, since the PR-system in the original speakers works really terribly, I opted to transform my 22AH487 speakers (right) into the 22AH468 speakers (left) which I sourced earlier. Since the boxes are identical other than the outer design, this was quite easy. I stripped the insides and removed the crossover.

Following this, I wanted to enhance the structural integrity of the box to reduce resonances. I did so by adding 2mm thick bitumen pads to all panels glued on with wood glue. And as I noticed that mainly the back panel vibrates a lot, I added a brace connecting the middle of the front and back panels.

Next, I added dampening. Some 5mm felt to the sides (and around the brace), and 15mm melamine foam to the back, top and bottom, attached with construction adhesive. Because I want to design my own crossover with DSP, I added a 8-pin DIN socket, connecting to the four drivers. I sealed this to the box with hot glue.

I didn't opt for integrating the crossover of the 22AH468 with a switch on the back (as I mentioned in my previous post) due to the complexity and because I can just connect the crossover externally if desired. I also considered using a Speakon connector, but opted for DIN 'cause Philips always used these types of connectors back then. Keeps the originality to some extent, I guess.

Now it's time for stuffing to increase the virtual box volume size. I went to IKEA and bought three SANDGRÄSMAL pillows, which have 100% polyester stuffing inside. It ended up being 717 g per speaker, which is about 1.3 lb/ft³.

'Upgrade' done! Knocking on the wood and tapping the woofer cones, I can clearly hear a difference compared to my other set 22AH468. Less internal reverberations and a higher pitched wood sound.

Now it's time to get an 8-channel amp and a DSP-capable board to design some crossovers. But that's for another day.

Wonder what y'all think of these modifications so far.

 

[DanielT]

Time for another short update. Really appreciate all the responses, I've already learned so much.

I ended up making a measurement jig and measuring the T/S parameters of the (supposedly 'better') AD8067/W4E woofer. Measuring with REW, dual added mass, net me these results:

Philips AD8067/W4E woofer​

Philips AD8066/W4 woofer​

So my theory is correct: the AD8067/W4E is better suited towards bass response. Great! However, playing around with box tuning in VituixCAD in the existing 35 L enclosure, I couldn't find any PR configuration that would net a significantly deeper bass response. The box needs to be vastly bigger to get any improvement. Makes sense considering the QTS. It appears that you all are correct. There's really no way, other than changing drivers, to make a PR system work in this box.

Anyways, since the PR-system in the original speakers works really terribly, I opted to transform my 22AH487 speakers (right) into the 22AH468 speakers (left) which I sourced earlier. Since the boxes are identical other than the outer design, this was quite easy. I stripped the insides and removed the crossover.

View attachment 470456View attachment 470457

Following this, I wanted to enhance the structural integrity of the box to reduce resonances. I did so by adding 2mm thick bitumen pads to all panels glued on with wood glue. And as I noticed that mainly the back panel vibrates a lot, I added a brace connecting the middle of the front and back panels.

View attachment 470458

Next, I added dampening. Some 5mm felt to the sides (and around the brace), and 15mm melamine foam to the back and top, attached with construction adhesive. Because I want to design my own crossover with DSP, I added a 8-pin DIN socket, connecting to the four drivers. I sealed this to the box with hot glue.

I didn't opt for integrating the crossover of the 22AH468 with a switch on the back (as I mentioned to in my previous post) due to the complexity and because I can just connect the crossover externally if desired. I also considered using a Speakon connector, but opted for DIN 'cause Philips always used these types of connectors back then. Keeps the originality to some extent, I guess.

View attachment 470459 View attachment 470461

Now it's time for stuffing to increase the virtual box volume size. I went to IKEA and bought three SANDGRÄSMAL pillows, which have 100% polyester stuffing inside. It ended up being 717 g per speaker, which is about 1.3 lb/ft³.

View attachment 470463

'Upgrade' done! Knocking on the wood and tapping the woofer cones, I can clearly hear a difference compared to my other set 22AH468. Less internal 'echoes' and a higher pitched wood sound.

View attachment 470468

Now it's time to get an 8-channel amp and a DSP-capable board to design some crossovers. But that's for another day.

Wonder what y'all think of these modifications so far.

Nice job. Adding brace to such large boxes seems like a sensible thing to do.

Fill with stuffing, experiment with how much you stuff in. Too much can kill the bass.

...then add one or more subwoofer / bass boxes with modern subbass drivers suitable for the purpose, in a period style that blends in with the looks of your speakers. But we have already addressed that aspect in the thread.

Or if you don't care about it looking to match in terms of style. Whatever subwoofers you want.